Stackable storage unit



FIG. 1 is a perspective view of a stackable storage unit illustrating my new design, the material shown in phantom merely illustrating the environment of use, and forming no part of my invention;

FIG. 2 is a right-side elevational view thereof, it being understood that the left-side elevational view and the rear elevational view are both identical thereto;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is an isometric view of the stackable storage unit of FIG. 1, but showing two additional units in broken lines for illustrative purposes only, which form no part of the claimed design. 

The ornamental design for the stackable storage unit, as shown and described. 